1. Field of the Invention
This invention relates to a pulsatile flow delivery apparatus which can produce an arterial pulsatile pressure wave form close to that produced by the natural heart.
2. Prior Art
Conventionally, a pulsatile roller pump as shown in FIG. 1 has been used for extracorporeal circulation during either cardiopulmonary bypass or extended cardiac support or assistance. The pump is based on the principle of intermittently switching on and off the rotation of an arm 3 bearing two or three milking rollers 3a moving inside a horse shoe shaped raceway 1 that holds a tube 2, thus milking the blood (or any fluid) intermittently, i.e., in a pulsatile fashion. The speed of rotation is set so as to obtain the desired minute output at the set pulse frequency.
The currently available pulsatile pump, however, has three main shortcomings whose solution are desirable.
As shown in FIG. 2, the pulse wave of the pulsatile roller pump is the resultant of the summation of the sequential milking of each of the rotating two (or three) rollers, thus the pulse wave contour is scalloped or indented. Because of the inertia of the system, since the rotation of the roller bearing arm 3 has to go from zero to the maximum speed of rotation as preset by the required output in a short period, the velocity of pressure change or ascent slope of the pressure wave (dp/dt) is relatively slow with a relatively narrow pulse pressure and far from the natural cardiac beat pulse wave contour. Thirdly at high pulse frequency rates, the intended pulsatile flow becomes almost a constant flow type perfusion, i.e., the pump can not follow high frequency pulse rates.